ONO 99

Up to eight players may take part. Each player picks a card from the deck, and the player drawing the highest-numbered card is the dealer. This person then deals four cards to each player, and places the remainder of the deck face down in the center of the table. The player to the dealer's left starts the hand by playing a numbered card face up in the center of the table and announces the number. They must then immediately draw the top card from the deck. Each subsequent player does likewise, announcing a new total by adding the value of their card to the previous player's total. Play continues clockwise around the table until one player causes the total to reach or exceed 99; that player immediately loses the hand.

In addition to cards numbered 2 through 10, five special types of cards are present in the deck, which may be used to attack opponents or benefit the player using them.

• Minus 10: Deducts 10 points. Negative totals are allowed; for example, if a Minus 10 is played when the total is 6, the next player faces a total of -4.
• Hold: Leaves the total unaffected.
• Reverse: Leaves the total unaffected and reverses the direction of play (clockwise to counter-clockwise, and vice versa). If only two players are in the game, it has the same effect as a Hold.
• Double Play: Leaves the total unaffected and forces the next player in sequence to take two complete turns. That player may immediately use a Hold or Reverse to force the player after them to play twice instead. A player who is required to do a Double Play may use a Double Play card on the second turn, but not the first.
• ONO 99: Immediately raises the total to 99, causing the player using it to lose the hand. Ordinarily, this card merely takes up space in a player's hand; however, since there are four of these cards in the deck, it is possible for one player to end up holding all of them and thus lose the hand on his/her next turn. An alternate rule allows this card to be played without penalty if the total ends in zero, in which case it functions identically to a Hold card.

If a player lays down a card, but fails to draw one before the next player in sequence completes their own turn, they are not allowed to replace the missing card. A player so affected can potentially be at a great disadvantage, especially if they are holding one or more ONO 99 cards. The player may correct the error by drawing a card before the next player in sequence completes a turn.

Each player is given three chips at the start of the game and must surrender one upon losing a hand; a player who loses a hand with no chips remaining is out of the game. The last remaining player is the winner.

A variation is to use a point-scoring system in which the player who loses the hand is charged with 25 points plus the value of their cards:

• Number cards: face value
• Hold, Reverse, Minus Ten, and Double Play cards: 15 points
• ONO 99 card: 20 points
• Penalty for a missing card: 15 points

A point limit is determined before the start of the game (500 is suggested). When a player's score reaches the limit, either the game ends and the player with the lowest score wins, or the player is eliminated and the game continues until only one player is remaining.